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Science 2 July 1965:
Vol. 149. no. 3679, pp. 67 - 69
DOI: 10.1126/science.149.3679.67
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Articles

Active Uptake of Sodium by Softshell Turtles (Trionyx spinifer)

William A. Dunson 1 and Robert D. Weymouth 1

1 Department of Zoology, University of Michigan, Ann Arbor 48104

Aquatic softshell turtles (Trionyx spinifer spinifer) show a net active uptake of sodium from solutions of this cation as dilute as S micromoles per liter. This probably occurs in the pharynx, a site of aquatic respiration. Inhibition of active sodium transport by low temperatures causes an extreme lowering of the sodium concentration in the plasma. Other fresh-water turtles may utilize this mechanism of ionic regulation. The ultrastructure of the pharyngeal villi is similar to that of frog skin and toad bladder.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)